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61.
Field LD Ramadan SA Pierens GK 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,155(1):64-71
Cyclic J cross polarisation (CYCLCROP) is a sensitive method for the noninvasive monitoring of (13)C distributions and fluxes. The PRAWN rotating frame Hartmann-Hahn mixing sequence ameliorates problems associated with sensitivity to Hartmann-Hahn mismatch and reduces RF power deposition. The combination of CYCLCROP with echo planar imaging (EPI) for spatial encoding of the proton detected carbon signal allows efficient use of the available signal to be made, permitting a significant improvement in the temporal resolution of any study. We report here on some initial experiments to demonstrate the feasibility of echo planar proton detected (13)C imaging using CYCLCROP based upon the PRAWN module, including the application of the technique to the measurement of transport and accumulation of (13)C-labelled sucrose in a castor bean seedling. Two methods that can be used to eliminate the effect of the J-splitting in the EP images are presented. In addition, a fast, image-based B(1) field-mapping method which may be used to quantitatively map the low frequency RF field in a dual resonant ((13)C/(1)H) probe is presented. The technique utilises the above described imaging method, permitting fully quantitative, 64x64 axial field maps to be generated in about a minute. 相似文献
62.
Brian Spencer Robert A Marr Edward Rockenstein Leslie Crews Anthony Adame Rewati Potkar Christina Patrick Fred H Gage Inder M Verma Eliezer Masliah 《BMC neuroscience》2008,9(1):109
Background
Proteolytic degradation has emerged as a key pathway involved in controlling levels of the Alzheimer's disease (AD)-associated amyloid-β (Aβ) peptide in the brain. The endopeptidase, neprilysin, has been implicated as a major Aβ degrading enzyme in mice and humans. Previous short and intermediate term studies have shown the potential therapeutic application of neprilysin by delivering this enzyme into the brain of APP transgenic mice using gene transfer with viral vectors. However the effects of long-term neprilysin gene transfer on other aspects of Aβ associated pathology have not been explored yet in APP transgenic mice. 相似文献63.
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We present Doppler resolution limited spectra of the P(J) and R(J) multiplets for J ≦ 10 of the 10-μm CO stretch band of 12CD316OH using a tunable diode laser. Relative frequencies within the multiplets accurate to ±0.0002–0.0005 cm?1 are obtained, but no absolute frequencies are given. We are able to assign most of the hindered rotation and K substructure in these multiplets. The assignments are based on analyses of Stark-difference spectra combined with the ground-state microwave data and the intensity variations which are expected theoretically. The ground and excited state A, K = 1 asymmetry splitting parameters are measured to be δ1″ = (8.5450 ± 0.0080) × 10?3cm?1 and δ1′ = (9.7706 ± 0.0080) × 10?3cm?1, respectively. The ground-state value agrees well with the microwave results. A rapid-scan system for recording data and a computer-aided technique for calibrating and plotting the spectra are described. 相似文献
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To explore the use of methoxymethyl groups to elaborate simple benzenoid precursors to more complex polyketide-derived natural products, the reaction of phenolmetoxymethyl ether -anion was investigated with a number of electrophiles. 相似文献
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Using a stereospecifically labelled precursor, the peroxide catalysed cyclisation of N--butyldihydrocinnamamide to the corresponding β-lactam was shown to proceed with complete loss of stereochemistry at the benzylic carbon atom. 相似文献